1) TWO PEOPLE WHO OWN ONE COURTYARD
QUESTION: The Mishnah (45b) presents a case of partners who own property (such as a courtyard) together who each made a Neder to prohibit himself from having Hana'ah from the other. The Rabanan rule that each partner is prohibited from entering the courtyard, since, by entering it, he will derive benefit from the other partner's share of the property. Rebbi Eliezer ben Yakov permits each partner to enter the courtyard, because wherever each one goes it can be said that he is walking on his own part of the courtyard.
The Gemara in Bava Kama (51b) explains that the Rabanan and Rebbi Eliezer ben Yakov disagree about whether Bereirah works. "Bereirah" refers to a retroactive clarification of the status of a past event based on an event which occurs in the future. The Rabanan maintain "Ein Bereirah," and thus when each partner uses the courtyard there is no retroactive clarification that the part that he is using now was the part he bought as his portion at the time of the original Kinyan. Consequently, he is using not only his portion but his friend's portion as well. Rebbi Eliezer ben Yakov maintains "Yesh Bereirah," and thus when each partner uses the courtyard there is retroactive clarification that the part that he is using now was the portion which he owned from the beginning. Accordingly, he is using only his portion and not his friend's.
In the Gemara, both Rav Huna and Rebbi Elazar rule in accordance with the view of Rebbi Eliezer ben Yakov, and this is the Halachah in practice.
The RAN (45b) cites the Rishonim who question the conclusion of the Gemara here that the Halachah follow the opinion of Rebbi Eliezer ben Yakov who rules "Yesh Bereirah." The Gemara in other places (Beitzah 38a) rules that "Ein Bereirah" in all laws that are mid'Oraisa (certainly the status of a Kinyan and the prohibition of a Neder are laws that are mid'Oraisa).
Various answers are suggested by the Rishonim. RABEINU TAM explains that the Halachah indeed is "Ein Bereirah," but the Gemara here rules like Rebbi Eliezer ben Yakov because of another consideration. The act of walking through someone else's property is considered "Vitur," a use of one's property which the owner allows and does not protest. Whether or not an act of "Vitur" is forbidden to one who is a Mudar Hana'ah is the subject of dispute. Rabeinu Tam asserts that the Halachah follows the opinion that "Vitur" is permitted to a Mudar Hana'ah, and thus in the case of the jointly-owned courtyard one partner may walk through his friend's portion even though he is not permitted to derive Hana'ah from his friend. (According to this approach, if one partner explicitly included in his Neder "walking upon my property," the other partner would be prohibited from walking in the courtyard because the Halachah with regard to Bereirah is "Ein Bereirah.")
The Rishonim reject Rabeinu Tam's answer because they maintain that the Halachah is that "Vitur" is prohibited to a Mudar Hana'ah, as a number of Sugyos imply.
The RASHBA (cited by the Cheshek Shlomo) and the RAMBAN (in Bava Kama 106a, cited by the Shalmei Nedarim; see also RE'EM cited by the Shitah Mekubetzes) explain that Rebbi Eliezer ben Yakov agrees that the Halachah is "Ein Bereirah" in matters that are mid'Oraisa. Here, however, he rules "Yesh Bereirah" because the prohibition of "Vitur" to a Mudar Hana'ah (which prohibits each partner from walking on the other's property) is only an Isur d'Rabanan (as implied by the Ran later, 48b, DH v'Zimnin), and the Halachah is "Yesh Bereirah" for matters that are mid'Rabanan. (According to this approach as well, if one partner explicitly included in his Neder "walking upon my property," the other partner would be prohibited from walking in the courtyard because the Isur d'Oraisa of the Neder prohibits walking through the property, and not just the Isur d'Rabanan of "Vitur," and even Rebbi Eliezer ben Yakov rules that "Ein Bereirah" for matters that are mid'Oraisa. Likewise, it is obvious why the Mishnah says that Rebbi Eliezer ben Yakov agrees that each partner is prohibited from setting up a millstone or raising chickens in the courtyard; such uses are not "Vitur" and thus they are Asur mid'Oraisa, and Rebbi Eliezer ben Yakov agrees that the Halachah is "Ein Bereirah" with regard to matters that are mid'Oraisa.)
(Indeed, this answer seems so straightforward that REBBI AKIVA EIGER in Mishnayos concludes with "Tzarich Iyun" on the Ran and other Rishonim who give different answers and understand that Rebbi Eliezer ben Yakov rules "Yesh Bereirah" even for matters that are mid'Oraisa. See Insights to Nedarim 32:1 for possible ways to explain why the case here involves a matter d'Oraisa.)
According to the other Rishonim, who say that Rebbi Eliezer ben Yakov indeed rules contrary to the ruling of the Gemara in Beitzah (38a) with regard to Bereirah, how can the two Halachic rulings be reconciled?
ANSWERS: A number of approaches to this question are given by the Rishonim, some of which will be reviewed here. To better understand the answers, one first must address how a partnership or joint-ownership ("Shutfus") works.
The RAN (45b) writes that it is impossible for two people to own an item jointly such that each person owns the entire item all of the time. An item can be owned only by one person at any given moment. If two people purchased an item together (each one paid half of the value of the item), what exactly does each one own?
The simple understanding is that each person owns half of the item. Hence, when two people buy a dividable commodity (such as a bushel of fruit or a large piece of land), each person owns half of the commodity and may force the other to split it up and take his share (Bava Basra 13a). However, when the commodity is not dividable (such as a small piece of land like a courtyard, an animal, or an Eved), how does the joint-ownership take effect?
Some explain that the joint-ownership works in that each person owns the entire item for half of the time (instead of owning half of the item for the entire time). Hence, if two people own an Eved together, for example, each one uses the Eved on alternating days (or whatever similar arrangement they make).
Alternatively, it could be that the joint-ownership works in that each person owns only half of the item, but since the item cannot be divided each owner is required to permit the other owner to use his share when he wants (at agreed-upon times). This arrangement can be understood in at least three ways. The first way to understand it is that when two people buy one indivisible item together, such as a small courtyard, each person owns half of the land, and he is entitled to use the other person's land because of a "Shibud" which obligates each partner to let the other use his portion. (According to this view, each partner may use the entire courtyard.)
The second way to understand this arrangement of joint-ownership is that when two people buy a courtyard together such that each owns half of the courtyard, ownership of half of the courtyard brings with it the automatic right to use the entire courtyard by virtue of the fact that the courtyard cannot be divided. It is not that one partner's share is "Meshubad" to the other's usage, but that each person's Kinyan of half of the courtyard means that he may use the entire courtyard, since it is impossible to make a Kinyan which is limited to half of the courtyard (since the courtyard is not dividable). In other words, when one person buys half of the courtyard, he acquires two things through the Kinyan: half of the value of the courtyard (so that when it is sold, he receives half of the profits), and the right to use the entire courtyard (but it is not because the other person has a "Shibud" to let him use the courtyard). (According to this view, too, each partner may use the entire courtyard.)
Finally, the joint-ownership of an indivisible commodity may work through Bereirah, according to the opinion that rules "Yesh Bereirah." Each person owns only half of the land, but when he uses any part of the land it becomes determined retroactively that this part of the land was the part that he bought. (According to this view, however, each partner may use only up to half of the courtyard at any given moment.)
Based on this introduction, the approaches which the Rishonim suggest for the Gemara here may be understood as follows.
(a) The RAMBAN (cited by the RAN on 45b and by the NIMUKEI YOSEF in Bava Kama 51b) explains that the reason why Rebbi Eliezer ben Yakov permits each partner to use the land is not because he rules "Yesh Bereirah." When each partner uses the land, there is no retroactive clarification that this is the part that he owns. When the Gemara in Bava Kama (51b) says that the Rabanan and Rebbi Eliezer ben Yakov argue about "Bereirah," it does not mean the Bereirah of retroactive clarification. Rather, the Gemara there means something entirely different by the word "Bereirah." (He adds that the Gemara occasionally uses a word in two different contexts with entirely different meanings.) When the Gemara says that Rebbi Eliezer ben Yakov permits each partner to use the courtyard because of "Bereirah," "Bereirah" means the right of each partner to use the entire courtyard. Each partner may choose any part of it and say that he is exercising his right that he bought (along with half of the value of the land) to use whatever part he wants. Rebbi Eliezer ben Yakov agrees, however, that there is no retroactive clarification of ownership.
The Ramban is saying that Rebbi Eliezer ben Yakov maintains that joint-ownership of an undividable commodity works according to the second way explained above. The Rabanan who argue with Rebbi Eliezer ben Yakov may understand that joint-ownership of such property works because of a "Shibud" (as the Ran on 45b explains) and not because of a Zechus that was included in the Kinyan, and since a Neder has the power to uproot a "Shibud" each partner is prohibited from using the courtyard.
(b) The RAN (46a) also explains that Rebbi Eliezer ben Yakov agrees that the Halachah is "Ein Bereirah." However, the form of Bereirah in this case is different from the form of Bereirah in the cases in which the Halachah is "Ein Bereirah." "Ein Bereirah" means that "it is not appropriate for a Kinyan to take effect in a way which leaves a doubt as to how it took effect." This means that the Kinyan must take effect at the same moment at which the action which accomplishes the Kinyan is performed (such as the act of giving a Get). The Kinyan cannot be left in an undecided state, to take effect after the act and dependent on future events, because the act which makes the Kinyan will no longer be present at that time. Accordingly, if at the moment the act is performed the Kinyan "does not know" where or how to take effect, the Kinyan does not take effect.
Here, however, the Kinyan takes effect completely at the moment the partners buy the land. The Kinyan takes effect with no doubts left unresolved: each partner owns half of the value of the land. The land, according to the Ran, is divided by time of usage, so that each person owns the entire land half of the time. The only thing which remains to be clarified is the minor detail of when each person owns the land. (As to how the ownership of the land can go back and forth between the two owners, this is the topic of the Sugya of "v'Acharecha l'Ploni"; see KETZOS HA'CHOSHEN 241:4 and 171:1). This detail -- since it is not intrinsic to how the Kinyan takes effect -- is able to be clarified through Bereirah even though, normally, Bereirah does not work. The day on which each partner uses the field in the future becomes clarified as the day for which his half-ownership of the value of the field entitled him to use the field. Hence, the Halachah in this case follows Rebbi Eliezer ben Yakov who says that such Bereirah works, and the Halachah also follows the opinion that Bereirah which affects the actual Kinyan (how it takes effect) does not work.
The Ran is saying that according to Rebbi Eliezer ben Yakov, a joint-ownership of an undividable commodity works through Bereirah (like the third way of understanding a joint-ownership, as explained above), but the Bereirah is the type which clarifies only a secondary detail about the Kinyan and not the type which clarifies a primary, inherent detail which the Kinyan needs in order to take effect.
The Rabanan, on the other hand, disagree and maintain that even such a form of Bereirah does not work. Rather, the joint-ownership of such property works because of a "Shibud" and not because Bereirah clarifies when each person's Kinyan applies. Since a Neder has the power to uproot a "Shibud," each partner is prohibited from using the courtyard.
HALACHAH: There are a number of practical differences between the Ran's way of understanding the view of Rebbi Eliezer ben Yakov and the Ramban's way. For example, REBBI AKIVA EIGER (Teshuvos #66) discusses whether a house owned jointly by a Jew and a Nochri needs a Mezuzah. According to the Ran, the house would need a Mezuzah because when the Jew lives there he owns it entirely. According to the Ramban, the house would not need a Mezuzah because even when one partner uses it the entire house belongs to both of them (that is, each owns half of the value of the house), and a house owned even partially by a Nochri does not require a Mezuzah. (See other practical differences cited by YOSEF DA'AS here and in TESHUVOS DOVEV MEISHARIM 1:36.)
The SHACH (YD 276:4) apparently follows the view of the Ramban, while the KETZOS HA'CHOSHEN (171:1) follows the view of the Ran.